《生物医学信号处理(双语)》精品课件.pptVIP

* * Zhongguo Liu_Biomedical Engineering_Shandong Univ. Chapter 4 HW 4.5 上一页 下一页 返 回 * * * * * * * * * * * * * * * 4.4 Discrete-Time Processing of Continuous-Time signals * 4.4 Discrete-Time Processing of Continuous-Time signals * C/D Converter Output of C/D Converter * D/C Converter Output of D/C Converter * 4.4.1 LTI DT Systems Is the system Linear Time-Invariant? 即采样时无频率混叠. 采样频率 * Linear and Time-Invariant Linear and time-invariant behavior of the system of Fig.4.10 depends on two factors: Firstly, the discrete-time system must be linear and time invariant. Secondly, the input signal must be bandlimited, and the sampling rate must be high enough to satisfy Nyquist Sampling Theorem.(避免频率混叠) * This is the effective frequency response of the overall LTI continuous- time system. 等效的连续时间系统必须是带限的. * Example 4.3 bulid a Ideal Continuous-Time Lowpass Filtering using a Discrete-Time Filter LTI DT System LTI CT System -π π Given Solution: * Example 4.3 Ideal Continuous-Time Lowpass Filtering using a Discrete-Time Filter interpretation of how this effective response is achieved.? Figure 4-12 * Example 4.3 Ideal Continuous-Time Lowpass Filtering using a Discrete-Time Filter interpretation of how this effective response is achieved.? Figure 4-12 等效连续低通滤波器频率响应 * Example 4.4: Discrete-Time Implementation of an Ideal Continuous-Time Bandlimited Differentiator Solution: Differentiator: Frequency response: The inputs are restricted to be bandlimited. For bandlimited signals, it is sufficient that: The corresponding DT system has frequency response: If inputs are bandlimited, 高于π/T的频率响应也用不到. * Example 4.4: Discrete-Time Implementation of an Ideal Continuous-Time Bandlimited Differentiator effective frequency response : frequency response for DT system : * Example 4.4: Discrete-Time Implementation of an Ideal Continuous-Time Bandlimited Differentiator frequency response for DT system : The corresponding impulse response : or equivalently, * 4.4.2 Impulse Invariance